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21 March 2010

BOBGRAM7 issued 22 March 2010

WEATHERGRAMYOTREPSIssued 22 Mar 2010Bob McDavitt's ideas for sailing around the South Pacific.

Disclaimer: Weather is a mix of pattern and chaos; these ideas come fromthe patterned world of weather maps, so please fine-tune to your place.Dates are in UTC unless otherwise stated.

I am a day later than usual this week, since I spend 9 hours drivingback to Auckland yesterday and decided to rest in the evening.

TROPICSNow that TOMAS and ULUI have taken away most of the convective energybuild-up in the South Pacific, it looks as though' we may be in for areasonable quiet period now. The South pacific Convergence Zone SPCZtoday stretches from Vanuatu to Fiji/Southern Tonga to south end ofSouthern Cooks. This zone is expected to drift north and weaken thisweek. Also, the forecast is for a build-up of convection in the centralCoral Sea, and maybe a low or a trough of light winds near New Caledoniaaround this weekend from Friday 26 to Sunday 28 March.

We had the equinox last Sunday, and as the sun is now overhead in theNorthern Hemisphere, it is interesting that a tropical depression hasdeveloped in the NW Pacific. This is expected to weaken to east ofPhilippines by Friday 27 March.

SUBTROPICAL RIDGE: HIGH cell is forecast to cross the Southern Bight on 23 March (WorldMeteorological day) and then cross the Tasman Sea/Northland area on 25to 27 March keeping the rain away. There will be an enhanced zone oftrade winds along 25S. This zone will extend eastwards all the way tothe date line as the High cell moves east. More fetch for more swellfor the Brissy coast.

The next HIGH cell is likely to take a more southern route, crossingTasmania on Friday 26 March and then the South Island on Sunday 28March, producing a squash zone of onshore easterly winds onto thesouthern North Island. Avoid.

TASMAN/NZDeep Southern ocean Low wandered close to Fiordland earlier today sothat its front was intense with 75 knot gusts and well over 100mm rainon the Southern Alps. The wind helped delay the cricket in Wellington.Front will weaken as it crosses the rest of NZ on Tuesday.

Another deep Southern Ocean Low is likely to wander north close to Otagoon Thursday. Its front should cross NZ on Wednesday preceded by strongNW winds and heavy alpine rain and followed by an unsettled westerlyflow.

Then, on Friday we are forecasting the front that will lead in a HIGHcell. It, too, will likely be heralded by intense Northwest wind andrain over south end of NZ, but this time it will be followed bysoutherlies and clearing weather - and not as cold as the last one(which gave many inland areas a frosty start to 18 March last week).